1. Field of the Invention
The invention relates to retention of turbine engine thru-bolt stud/nut interface retention. Apparatus and methods of the invention retain thru-bolt stud/nut remnants within the confines of the affected rotor disc, in an unforeseeable event that a thru-bolt fractures, so that they do not migrate into the engine's gas flow path. More particularly, a housing coupled to the rotor envelops the projecting thru-bolt stud, so that the stud/nut remnant is captured by the housing.
2. Description of the Prior Art
Known gas and steam turbine engines have rotors comprising a plurality of serially aligned rotor discs with a circumferentially spaced array of axially aligned rotor disc bolt hole cavities. The rotor discs are axially retained by thru-bolts that are inserted in the axially aligned disc bolt hole cavities from one axial end of the rotor. The known exemplary combustion turbine engine 20, shown schematically FIGS. 1 and 2, has a compressor section 22, a combustor section 24 and a turbine section 26. Rotor 28 has a rotor shaft 30. The exemplary compressor section of the rotor 28 has an axially aligned stack of rotor discs 32 that are retained by compressive thru-bolts 34 with male threaded stud ends 36 and mating nuts 40 on both ends of the bolt. After torqueing the thru-bolts to a desired elongation for establishing compressive force on the rotor disc 32 stack, a thru-bolt stud tip 38 projects outwardly from the stud 36/nut 40 interface. In the event that a thru-bolt breaks, it shears off perpendicularly across the threaded portion 36 approximately along a line defining nut 40 contact with the rotor disc axial face 33. After the breakage, the rotor 28 stiffness changes, causing the engine 20 operational monitoring system to alarm the condition and trip (stop) service operation. However, notwithstanding the service operation trip, the broken stud 36/nut40 interface remnant is susceptible to migration through the turbine engine 20 flow path, risking domestic object damage to the engine internal components.